The purpose of the project is to determine whether the standardized hypoglycemia created during the hypoglycemic clamp can be used to more safely and accurately assess pituitary function than the standard insulin tolerance test. To complete the study, normal control subjects will undergo both hypoglycemic clamps and insulin tolerance tests to determine hormonal response and symptom scores. Norms for hormonal responses will then be determined for both young and old adults. Subjects with known hypopitiitarism will also be evaluated to determine whether the clamp test can be performed safely and accurately in such subjects.